Mix together dry ingredients - cocoa, flour, baking powder and salt. Set aside.
Using a hand mixer, mix sugar and melted butter. Add eggs and Irish Cream. Mix.
Slowly add dry ingredients while mixing.
Line a 9x9 baking dish with foil, press foil down firmly into the dish. Spray with non-stick.
Pour batter into prepared dish and spread evenly.
Bake at 350° for 30-35 minutes. (until a toothpick can be inserted a removed clean)
Allow brownies to cool before frosting. Once cooled and frosted, remove the foil and brownies from baking dish. Carefully peel foil away from brownies and slice into 9 pieces.
Frosting
Combine butter and powdered sugar. Mix for 3-4 minutes, until light and fluffy.
Add Irish cream and cocoa powder. Mix for 1 more minute.